/Engine/Source/Runtime/Engine/Classes/Camera/CameraModifier.h
Called per tick that the modifier is active to allow Blueprinted modifiers to modify the camera's transform. Scaling by Alpha happens after this in code, so no need to deal with that in the blueprint.
void BlueprintModifyCamera ( float DeltaTime, FVector ViewLocation, FRotator ViewRotation, float FOV, FVector & NewViewLocation, FRotator & NewViewRotation, float & NewFOV )